Magnetically guided catheter

ABSTRACT

A catheter comprising a flexible tubing having a proximal end and a distal end. An electrode assembly is attached to the distal end of the flexible tubing. The electrode assembly includes an electrically conductive tip electrode and a coupler which is connected between the tip electrode and the distal end of the flexible tubing. The coupler and the tip electrode are coupled by an interlocking connection. A first magnet is at least partially housed in the coupler. A fluid lumen extends through the flexible tubing to the coupler. The fluid lumen extends completely through the first magnet and connects to at least one port formed in the electrode assembly. A second magnet is spaced from the electrode assembly along a longitudinal axis of the tubing. The first magnet and the second magnet are responsive to an external magnetic field to selectively position and guide the electrode assembly within a body of a patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Provisional Application No.60/947,791, filed 3 Jul. 2007 (the '791 application), and internationalpatent application numbers PCT/US2008/069,241 (the '241 application)PCT/2008/069,248 (the '248 application) both of which were filed 3 Jul.2008, and U.S. non-provisional application Ser. No. 12/667,338 filed 30Dec. 2009 (the '338 application). This application is also acontinuation-in-part of Ser. No. 12/167,736, filed 3 Jul. 2008 now U.S.Pat. No. 8,206,404 (the '736 application), which in turn claims thebenefit of the '791 application and the '241 application. The entirecontents of each of the '791, the '241, the '248, the '338, and the '736applications are hereby incorporated by reference as though fully setforth herein.

BACKGROUND OF THE INVENTION

a. Field of the Invention

This invention relates generally to medical instruments, and, morespecifically, to a navigable catheter device positionable within a bodyof a patient using an externally applied magnetic field.

b. Background Art

Catheters are flexible, tubular devices that are widely used byphysicians performing medical procedures to gain access into interiorregions of the body. Careful and precise positioning of the catheterswithin the body is important to successfully completing such medicalprocedures. This is particularly so when catheters are used to produceemissions of energy within the body during tissue ablation procedures.Conventionally, positioning of such catheters was accomplished withmechanically steerable devices. More recently, magnetically navigablecatheter devices have been developed that are navigated with anexternally applied magnetic field. Such catheter devices can be complexin their construction, and therefore are difficult to manufacture andrelatively expensive to produce.

Magnetic stereotactic systems have been developed that are particularlyadvantageous for positioning of catheters, as well as other devices,into areas of the body that were previously inaccessible. The magneticfields and gradients are generated to precisely control the position ofthe catheter within the patient's body. Once correctly positioned,physicians may operate the catheter, for example, to ablate tissue tointerrupt potentially pathogenic heart rhythms or to clear a passage inthe body, for example. Specifically, such stereotactic systems monitorthe position of a tip of the catheter in response to the appliedmagnetic fields. Using well established feedback and control algorithmsthe catheter tip may be guided to and positioned in a desired locationwithin the patient's body.

The magnetic response of the catheter can be a limitation on the precisecontrol of a catheter when used with such magnetic guidance systems.Improvements in catheters utilized with magnetic guidance and controlsystems, such as stereotactic systems, are desired. Specifically, a lowcost, yet high performance magnetically guided catheter is desirable.

BRIEF SUMMARY OF THE INVENTION

In various embodiments, magnetic guided catheters are disclosed that aremanufacturable at relatively low cost while providing high performancewhen used with, for example, magnetic stereotactic systems.

In one embodiment, a catheter is provided that includes a flexibletubing having a proximal end and a distal end. An electrode assembly isattached to the distal end of the flexible tubing. The electrodeassembly includes an electrically conductive tip electrode and a couplerwhich is connected between the tip electrode and the distal end of theflexible tubing. The coupler and the tip electrode are coupled by aninterlocking connection. A first magnet is at least partially housed inthe coupler. A fluid lumen extends through the flexible tubing to thecoupler. The fluid lumen extends completely through the first magnet andconnects to at least one port formed in the electrode assembly. A secondmagnet is spaced from the electrode assembly along a longitudinal axisof the tubing. The first magnet and the second magnet are responsive toan external magnetic field to selectively position and guide theelectrode assembly within a body of a patient.

In another embodiment, a catheter is provided that includes an electrodeassembly attached to the distal end of the flexible tubing and includinga first magnet at least partially therein. The electrode assemblyincludes an electrically conductive tip electrode and an internalcoupler which is connected between the tip electrode and the distal endof the flexible tubing. A second magnet is spaced from the electrodeassembly along a longitudinal axis of the tubing. The flexible tubing isa unitary tubing, and the second magnet is pushed inside the flexibletubing after the unitary flexible tubing is formed. The first magnet andthe second magnet are responsive to an external magnetic field toselectively position and guide the electrode assembly within a body of apatient.

In yet another embodiment, a catheter is provided that includes anelectrode assembly attached to the distal end of the flexible tubing andincludes a first magnet at least partially therein. The electrodeassembly includes an electrically conductive tip electrode and aninternal coupler which is connected between the tip electrode and thedistal end of the flexible tubing A second magnet is spaced from theelectrode assembly along a longitudinal axis of the tubing. The flexibletubing is a unitary tubing, and the second magnet is pushed inside theflexible tubing after the unitary flexible tubing is formed. The firstmagnet and the second magnet are responsive to an external magneticfield to selectively position and guide the electrode assembly within abody of a patient.

Still other features of magnetic guided catheters are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first exemplary magnetic guided catheter.

FIG. 2 is a magnified view of a distal end portion of the catheter shownin FIG. 1.

FIG. 3 is a cross sectional view of the distal end portion shown in FIG.2.

FIG. 4 is a magnified cross sectional view of the electrode tip assemblyshown in FIGS. 2 and 3.

FIG. 5 is an exploded view of the distal end portion shown in FIG. 2 ofthe catheter shown in FIG. 1.

FIG. 6 illustrates an enlarged view of an alternate connecting structurefor the attachment of the tube portions to the magnets.

FIG. 7 illustrates a second exemplary embodiment of a magnetically guidecatheter.

FIG. 8 illustrates an electrode assembly for the catheter shown in FIG.7.

FIG. 9 is a magnified assembly view of a portion of the tip assemblyshown in FIG. 8.

FIG. 10 illustrates a magnet assembly for the catheter shown in FIG. 7.

FIG. 11 illustrates a distal portion of the catheter shown in FIG. 7 inan operating position.

FIG. 12 illustrates a third exemplary embodiment of a distal portion ofa magnetically guided catheter including a flexible tip and cylindricalmagnets.

FIG. 13 illustrates an exemplary manufacturing process for themagnetically guided catheter.

FIGS. 14 a-b illustrate another exemplary magnetic guided catheter,wherein FIG. 14 b is a magnified view of the distal end portion shown inFIG. 14 a.

FIG. 15 a is a cross sectional side view of the distal end portion ofthe magnetic guided catheter shown in FIGS. 14 a-b, and FIG. 15 b is across sectional view taken along lines A-A in FIG. 15 a.

FIGS. 16 a and 16 b illustrate the distal end portion of the magneticguided catheter shown in FIGS. 14 a-b, wherein (a) is a firstperspective view, and (b) is a second perspective view with partialcut-away.

FIGS. 17 a-c illustrate exemplary assembly of the different sections orportions of the magnetic guided catheter shown in FIGS. 14 a-b.

FIGS. 18 a-b illustrate exemplary assembly of magnets in the magneticguided catheter shown in FIGS. 14 a-b.

FIG. 19 illustrates exemplary assembly of a tip electrode to the distalend portion of the magnetic guided catheter shown in FIGS. 14 a-b.

DETAILED DESCRIPTION OF THE INVENTION

Many specific details of certain embodiments of the invention are setforth in the following description in order to provide a thoroughunderstanding of such embodiments. One skilled in the art, however, willunderstand that the present invention may have additional embodiments,or that the present invention may be practiced without several of thedetails described in the following description.

FIG. 1 illustrates a first exemplary non-steerable, single-usemagnetically guided catheter 100 generally including a flexible outertube, or tubing, 102, a tip assembly 104, positioning magnets 106 and108 separately provided from and spaced from tip assembly 104, a Yconnector 110, a leer device 117, and an electrical connector 114. Luerdevice 117 is used to open or dose a flow path so that fluid is passedthrough Y-connector 110 and tubing 102 to tip assembly 104 forirrigation purposes. Electrical connector 114 establishes electricalconnection with a power source (not shown) that operates electrodes oftip assembly 104 to perform, for example, ablation procedures, mappingor pacing procedures, or to perform other aspects of a medicalprocedure.

Although it will become evident that aspects of exemplary catheter 100are applicable to a variety of medical procedures and end uses, theinvention will be described principally in the context of a specificexample of a magnetically guided catheter. Specifically, catheter 100,as shown in FIG. 1, is believed to be particularly advantageous as anablation catheter for creating endocardial lesions during cardiacablation procedures to treat arrhythmias, and also for cardiacelectrophysiological mapping and delivering diagnostic pacing stimuli.However, the invention and the appended claims are not intended to belimited to any specific example, including but not limited to specificexamples or embodiments described herein, except when explicitly definedas such in the appended claims.

Y-connector 110 separates an inner tube 116 from electrical lead wires(not shown) extending between tip assembly 104 and electrical connector114. More specifically, tube 116 and the lead wires forward ofY-connector 110 pass internally through outer tube 102, while aft ofY-connector 110, inner tube 116 and leads for the lead wires are exposedand separated for connection to a fluid source (not shown) and the powersource, respectively. In one embodiment, electrical connector 114 is aknown connector configured to engage the power source or a power supplywith, for example, a plug-in connection. One suitable electricalconnector is a 14 pin REDEL® plastic connector commercially availablefrom LEMO of Rohnert Park, Calif., although other connectors fromvarious manufacturers may likewise be utilized.

Outer tube 102 includes a proximal end 118 coupled to Y-connector 110, adistal end 120 coupled to tip assembly 104, and an axial lengthextending between proximal end 118 and distal end 120. In oneembodiment, flexible tubing 102 is fabricated according to knownprocesses, such as multilayer processing including extrusion processes,mandrel-based processes and combinations thereof from any suitabletubing material known in the art of medical instruments, such asengineered nylon resins and plastics, including but not limited toPEBAX® tubing of Ato Fina Chemicals, France.

In an exemplary embodiment tubing 102 is fabricated from a first tubingmaterial defining a first portion 122 of tubing 102 between Y connector110 and magnet 108, a second tubing material defining a second portion124 of tubing 102 between magnet 106 and magnet 108, and a third tubingmaterial defining a third portion 126 of tubing 102 extending betweenmagnet 106 and tip assembly 104. In an exemplary embodiment, firstportion 122, second portion 124 and/or third portion 126 are fabricatedfrom different materials and grades of materials for enhancedperformance of tubing 102 in use of catheter assembly 100. Tubing 102,by virtue of portions 122, 124, and 126 having varying flexibleproperties, is sometimes referred to as a multi-flexible tube.

For example, in one embodiment, the first material defining firstportion 122 of tubing 102 is a comparatively rigid and kink resistantbraided material. First portion 122 is formed with different portions ofbraided material, semi-soft material, and soft material fused to oneanother so that first portion 122 becomes increasingly flexible alongthe axial length as first portion 122 approaches magnet 108. The secondmaterial defining second portion 124 of tubing 102, and the thirdmaterial defining third portion 126 of tubing 102 is a soft and flexiblematerial having approximately equal flexible properties. In theillustrated embodiment, each of tubing portions 122, 124, and 126between tip assembly 104 and magnets 106 and 108 share a common outsidediameter of, for example, 7 French, although in other embodiments,tubing portions 122, 124 and 126 have varied diameters.

As shown in FIG. 1, first portion 122 extends for a majority of theaxial length of tubing 102 between proximal end portion 118 and distalend portion 120. Second portion 124 of tubing 102 extends for a shorterlength than the length of first portion 122, and third portion 126 oftubing 102 extends for a length that is shorter than the length ofsecond portion 124. By way of example only, in a specific embodimentfirst portion 122 extends for an axial length of about 126.3 cm, secondportion 124 extends for an axial length of about 2.2 cm, and thirdportion 126 extends for an axial length of about 0.8 cm, although otherrelative lengths of the tube portions may likewise be employed in otherembodiments. The different relative lengths of tube portions 122, 124and 126, as well as the different flexible properties of tube portions122, 124 and 126, allow tip assembly 104 to be more precisely positionedwithin a patient's body, while also avoiding problems of kinks andexcessive deflection of tubing 102 along the majority of its lengthduring use and handling.

As another consequence of tubing sections 124 and 126 having an unequallength, magnet 106 is spaced a first distance from tip assembly 104, andmagnet 108 is spaced a second, greater distance from magnet 106 sincetubing portion 124 is longer than tubing portion 126. Due to the spacingof magnets 106 and 108 relative to one another and also to tip assembly104, which as explained below also includes a positioning magnet (notshown in FIG. 1), the spacing of magnets 106 and 108 permits positioningadjustment of tip assembly 104 in response to variations in anexternally applied magnetic field that may otherwise not be possible, ifmagnets 106 and 108 were provided in an equal or uniform spaced relationto one another. It is contemplated, however, that in another embodiment,tip assembly 104, magnet 106 and magnet 108 are equally spaced from oneanother.

In operation, a distal end portion 128 of catheter 100 including tipassembly 104 is navigated to a site in the body where a medicalprocedure, such as an atrial mapping, pacing and/or ablation are tooccur. Distal end portion 128 may extend, for example, into a heartchamber of a patient. Once distal end portion 128 is in the heartchamber, a magnetic field is applied to provide an orienting force todistal end portion 128, causing the tip positioning magnet and magnets106 and 108 to respond to the applied magnetic field and flex tubingportions 124 and 122 to precisely position tip assembly 104 forperformance of the procedure at a specific location. The magnetic fieldsused to orient tip assembly 104 are, in one embodiment, generated with amagnetic stereotactic system (not shown). Such stereotactic systems areknown and are commercially available from, for example, Stereotaxis ofSt. Louis, Mo. Such systems may include movable source magnets outsidethe body of the patient, and operative details of such systems aredisclosed in, for example, U.S. Pat. Nos. 6,475,223 and 6,755,816, thedisclosures of which are hereby incorporated by reference in theirentirety. While catheter 100 is advantageous for use with a stereotacticsystem, it is contemplated that magnetic fields and gradients to deflectcatheter tip assembly 104 may alternatively be generated by othersystems and techniques if desired.

FIG. 2 is a magnified view of distal end portion 128 of catheter 100shown in FIG. 1. Tip assembly 104 is coupled to a first end 130 of tubeportion 126 and magnet 106 is coupled to a second end 132 of tubeportion 126. A first end 134 of tube portion 124 is coupled to magnet106 and a second end 136 of tube portion 124 is coupled to magnet 108. Afirst end 138 of tube portion 122 is coupled to magnet 108, and a secondend (not shown in FIG. 2) of tube portion 122 is coupled to connector110 (shown in FIG. 1). As shown in FIG. 2, tip assembly 104 includesirrigation ports or openings 140 for passage of fluid from within tubing102 (shown in FIG. 1) to an exterior of tip assembly 104 when located inthe body of a patient.

FIG. 3 is a cross sectional view of distal end portion 128 wherein innertube 116 defines a central lumen 142 extending through each tube portion122, 124, and 126, and also through central bores formed in magnets 106and 108. Inner tube 116 has an outer diameter that is smaller than aninner diameter of tubing 102 and its portions 122, 124, and 126 suchthat space extends between an outer surface of inner tube 116 and aninner surface of tubing 102. In one embodiment, this space is used toaccommodate lead wires for electrical components of tip assembly 104.

Tip assembly 104 also includes a positioning magnet 144 having aninternal bore 146 passing therethrough. Inner tube 116 passes throughcentral bore 146 in magnet 144. Central lumen 142 is in fluidcommunication with luer 117 (shown in FIG. 1) on one end and withirrigation ports 140 extending through tip assembly 104 at the otherend. Thus, an irrigation fluid, such as saline, may be injected throughdistal end portion 128. Inner tube 116 may be, for example, a braidedpolyimide tube that maintains the flowpath through lumen 142 in allorientations of tip assembly 104, without compromising the flexibilityof tubing 102.

FIG. 4 is a magnified cross sectional view of tip assembly 104. In anexemplary embodiment tip assembly 104 includes a tip electrode 150, acoupler 152, a band electrode 154, positioning magnet 144, and atemperature sensor 156. Lead wires 158, 160 extend to tip electrode 150,and to band electrode 154 on first respective ends 162, 164 thereof, andto connector 114 (shown in FIG. 1) on second ends (not shown) so thatelectrodes 150 and 154 may be energized by a power source (not shown).

In the exemplary embodiment, tip electrode 150 may be, for example an 8Fr hemispherical-shaped tip electrode that is 2 mm in length. In otherembodiments, other sizes of tip electrodes may be utilized, includingbut not limited to 4 mm or 8 mm tip electrodes. Tip electrode 150 isformed with a plurality of openings that form irrigation ports 140 forsaline irrigation. In the exemplary embodiment, tip electrode 150 isfabricated from 90% platinum and 10% iridium, or other materials knownin the art such that tip electrode 150 is viewable under fluoroscopicexposure. While formed as an integral unit, tip electrode 150 mayinclude multiple electrode elements, such as ring electrodes forelectrophysiological mapping purposes, spaced from one another bydielectric materials as is known in the art.

Coupler 152 is a generally cylindrical, electrically nonconductivemember. It is typically made of a polymer such as PEEK™, which isrelatively rigid compared to rubber and has a limited amount offlexibility and resiliency to form a snap-fit connection, for example.Tip electrode 150 is formed with an annular projection 166 on its outersurface that engages a groove 168 within a first end 170 of coupler 152to form a snap-fit, interlocking connection. Alternatively, any matingconfiguration of tip assembly 104 and coupler 152 may be used. Coupler152 includes a second end 172 that is fitted within first end 130 oftube portion 126. Additionally, or alternatively thereto, first end 170of coupler 152 is adhered to tip electrode 150. Second end 172 ofcoupler 152 is adhered to the inner diameter of tube portion 126. Heatshrink techniques or adhesives may also be utilized to permanentlyattach coupler 152 to tube portion 126 and/or tip electrode 150.Positioning magnet 144 is disposed in a cavity which is formed at leastpartially inside the coupler 152 and which may be formed partiallyinside coupler 152 and partially inside tip electrode 150. Coupler 152houses positioning magnet 144 in tip assembly 104 and supports optionalband electrode 154, is more rigid than flexible tubing 102, and providesa convenient and reliable connection between tip electrode 150 and thirdportion 126 of flexible tubing 102.

Band electrode 154 is, in one embodiment, an 8 Fr ring-shaped bandelectrode that is for example, 2 mm in length, and spaced from tipelectrode 150 by a predetermined distance of 2 mm. Band electrode 154is, in one embodiment, fabricated from the same material as or adifferent material from tip electrode 150 and is attached to an outersurface of coupler 152.

In one embodiment, tip positioning magnet 144 is a generally cylindricalshaped permanent magnet fabricated from a known magnetic material, suchas neodymium-iron boron-45 (NdFeB-45). Alternatively, magnet 144 isformed from other materials and may have shapes different from theelongated cylindrical shape illustrated.

As shown in FIG. 4, magnet 144 includes an axially extending recess, orgroove, 176 formed into an exterior of magnet 144. Lead wires 158, 160,and a lead wire 178 for temperature sensor 156 pass through recess 176in a space defined by recess 176 and an inner surface of coupler 152.Temperature sensor 156 is, in one embodiment, a thermocouple typetemperature sensor, and lead wires 158, 160, and 178 are, for example,38 AWG wires having quad polyimide insulation.

Tip assembly 104 is particularly suited for ablation procedures whereinelectrodes 150 and 154 are energized to deliver radio frequency waves atthe site of an abnormal electrical pathway in the body. Radiofrequency(RF) energy may therefore be applied to biological tissue in proximityto tip assembly 104. Ablation procedures are typically used, forexample, within the interior chambers of the heart to thermally ablatecardiac tissue. Electrodes 150 and 154 may additionally be operated torecord intracardiac signals and to provide pacing signals.

FIG. 5 is an exploded view of catheter distal end portion 128 (shown inFIG. 1). Magnets 106 and 108 are each permanent magnets formed from, forexample, neodymium-iron Boron-45 (NdFeB-45) into an elongated tubularshape.

As shown in FIG. 5, second end 132 of tube portion 126, first and secondends 134, 136 of tube portion 124, and first end 138 of tube portion 122are formed into outwardly flared sockets 182, 184, 186 and 188. Magnet106 is received in socket 182 of tube second end 132 and socket 184 oftube portion first end 134. Magnet 108 is received in socket 186 of tubeportion second end 136 and socket 188 of tube portion first end 138. Inthe exemplary embodiment, sockets 182, 184, 186, and 188 are formed witha flaring tool and extend, for example, an axial length of about 2.5 mm.Sockets 182, 184, 186, and 188 are, in the exemplary embodiment, adheredto magnets 106 and 108, respectively, and heat shrunk to fuse sockets182 and 184 to magnet 106 and sockets 186 and 188 to magnet 108. Inanother embodiment, sockets 182, 184, 186, and 188 are maintained inposition with a friction fit. In the exemplary embodiment, adjacent tubeends 132 and 134 as well as adjacent tube ends 136 and 138 contact eachother and, in a particular embodiment, are fused to each other.

Tube portions 122, 124, and 126 have an outer diameter, at locationsother than sockets 182, 184, 186, and 188, that is smaller than theouter diameter of tube portions 122, 124, and 126 at the location ofsockets 182, 184, 186, and 188. In one embodiment, the outer diameter ofmagnets 106 and 108 is the same as, or larger than, the outer diameterof tube portions 122, 124, and 126 at locations other than sockets 182,184, 186, and 188. The larger diameter magnets are able to provide anenhanced response for positioning of catheter 100 (shown in FIG. 1) withexternally applied magnetic fields.

FIG. 6 illustrates an enlarged view of an alternate connecting structurefor the attachment of tube portions 126 and 124 to magnet 106. As shownin FIG. 6, a sleeve member 190 extends over sockets 182 and 184 andforms a smooth outer surface for a transition 192 from tube portion 126over magnet 106 to tube portion 124. Sheath 190 is, in one embodiment,fabricated from a thin tube of a polyimide material, or any othermaterial that provides a low coefficient of friction.

Although only three tube portions 122, 124, and 126 and two magnets 106and 108 spaced from tip assembly 104 are shown in FIGS. 1-6, it shouldbe understood that fewer than, or more than three tube portions and twomagnets could be used without departing from the spirit of thehereinabove described catheter.

FIGS. 7 through 11 illustrate a second exemplary embodiment of amagnetically guided catheter 200 that is similar in many aspects tocatheter 100 described above. Like components and features of catheter100 are indicated with like reference numbers in FIGS. 7 through 11.Unlike catheter 100, catheter 200 includes a distal end portion 202 thatis different from tip assembly 104 described above. Distal end portion202 includes magnets 204 and 206 (instead of magnets 106 and 108),rounded tip electrode 208, and tip element 210.

FIG. 8 illustrates distal end portion 202 including a tip assembly 212that includes rounded tip electrode 208 and tip element 210. Tip element210 is a flexible member that allows tip assembly 212 to flex, bend ordeflect along its axial length to, for example, different operatingpositions 214 and 216 (shown in phantom in FIG. 8) in addition to thein-line configuration shown in solid lines in FIG. 8 wherein the tip isstraight and generally linear along a longitudinal axis 218.

Tip assembly 212 also includes a coupler 220 that joins tip element 210to tube portion 126, a band electrode 154, and a positioning magnet 222provided internal to tip assembly 212. In the exemplary embodiment, tipelectrode 208 may be, for example an Fr hemispherical-shaped tipelectrode that is 2 mm in length. In other embodiments, other sizes oftip electrodes may be utilized, including but not limited to 4 mm or 8mm tip electrodes. Tip electrode 208 is formed with a plurality ofopenings that form irrigation ports 224 for saline irrigation. In theexemplary embodiment, tip electrode 208 is fabricated from 90% platinumand 10% iridium, or other materials known in the art such that tipelectrode 208 is viewable under fluoroscopic exposure. While formed asan integral unit, tip electrode 208 may include multiple electrodeelements, such as ring electrodes for electrophysiological mappingpurposes, spaced from one another by dielectric materials as is known inthe art,

Coupler 220 is a generally cylindrical, electrically nonconductivemember. It is typically made of a polymer such as PEEK™, which isrelatively rigid compared to rubber and has a limited amount offlexibility and resiliency to form a snap-fit connection, for example.Coupler 220 is connected at a first end 226 to tip element 210 and at asecond end 228 to first end 130 of tube portion 126. Coupler 220 is, inone embodiment, engaged to tip element 210 with a snap-fit, interlockingengagement similar to coupler 152 in FIG. 4. Additionally, oralternatively thereto, coupler 220 is adhered to tip element 210. Inaddition, coupler 220 is adhered to an inner section of tube portion126. Heat shrink techniques may also be utilized to permanently attachcoupler 220 to tube portion 126 and/or tip element 210. Positioningmagnet 222 is disposed in a cavity which is formed at least partiallyinside coupler 220 and which may be formed partially inside coupler 220and partially inside tip element 210. Coupler 220 houses positioningmagnet 222 in tip assembly 212 and supports optional band electrode 154,is more rigid than flexible tubing 102, and provides a convenient andreliable connection between tip element 210 and third portion 126 offlexible tubing 102.

Band electrode 154 is, in one embodiment, an 8 Fr ring-shaped bandelectrode that is for example, 2 mm in length, and spaced from tipelectrode 208 by a predetermined distance of 2 mm, Band electrode 154is, in one embodiment, fabricated from the same material as or adifferent material from tip electrode 208 and is attached to an outersurface of coupler 220.

In one embodiment, tip positioning magnet 222 is a generally cylindricalshaped permanent magnet fabricated from a known magnetic material, suchas neodymium-iron boron-45 (NdFeB-45). Alternatively, magnet 222 isformed from other materials and may have shapes different from theelongated cylindrical shape illustrated.

FIG. 9 illustrates exemplary tip element 210 in further detail. In theexemplary embodiment, tip element 210 is comprised of a single memberthat is formed into a helix, or spiral, and extends from tip electrode208 to coupler 220. Tip element 210 includes a helically shaped body 230having alternately spaced projections 232 extending away from body 230in opposite directions from one another along the length of the helix.That is, a first set of projections 234 extends distally, i.e., towardstip electrode 208, and a second set of projections 236 extendsproximally, i.e., away from tip electrode 208. The first set ofprojections 234 are staggered or offset from the second set ofprojections 236 such that the first set of projections 234 are offsetfrom, and positioned between, the second set of projections 236.

Recesses 238 extend between projections 232 and are complementary inshape to an outer contour of projections 232, but inversely shaped fromprojections 232. In the illustrated embodiment, projections 232, andrecesses 238, are trapezoidal in shape, although it is contemplated thatother shapes could likewise be utilized in alternative embodiments.

Tip element 210 is fabricated such that projections 232 from one sectionof body 230 extend into, and are captured within, recesses 238 from anadjacent section of body 230 to form an interlocking arrangement. Due toprojections 232 being complementary in shape to recesses 238 and thusdefining sockets or compartments for projections 232, projections 232are movable only a defined distance within recesses 238. In particular,and as shown in FIG. 9, tip element 210 is positionable to create aspace or gap 240 between leading edges of projections 232 and inneredges of recesses 238. Projections 232 and recesses 238 of tip element210 extend completely along the length of body 230 and, in oneembodiment, are uniformly spaced and sized around a perimeter of body230. Alternatively, projections 232 and recesses 238 may be differentlysized and/or spaced around the perimeter of body 230.

As a consequence of gaps 240, and also the complementary shapes ofprojections 232 and recesses 238, projections 232 are provided a freedomof movement within recesses 238 without being able to be removedtherefrom. Accordingly, sections of tip element 210 can move toward andaway from each other a defined distance to decrease and increase,respectively, gaps 240. It is thus possible for sections of tip element210 to move relative to one another in multiple ways. For example, tipelement 210 may be compressed so that all of gaps 240 are closed, ornearly closed, to reduce the longitudinal length of tip assembly 212 bythe cumulative dimensions of gaps 240 along a longitudinal axis 242.Additionally, sections of tip element 210 may exhibit cascaded orsequential movement along longitudinal axis 242 wherein some gaps 240are dosed along longitudinal axis 242 while other gaps remain open,either partially or fully. This allows gaps 240 between any adjacentsections of tip element 210 to be opened or closed in an uneven ornon-uniform manner. As such, gaps 240 on one side of tip assembly 212may be dosed while gaps 240 on the other side of tip assembly 212 may beopened. The result of this configuration is that tip assembly 212 curvesin the direction of the closed gaps 240 and away from the direction ofthe opened gaps 240. It can be appreciated that movement in vertical andhorizontal planes may simultaneously occur due to the interlockingconstruction of tip element 210 to flex and deflect tip assembly 212 toa practically unlimited number of positions. Tip assembly 212 maydeflect in the manner described due to, for example, impact forces on anouter surface of tip assembly 212 in use and may also, in whole or inpart, be the result of the magnetic response of positioning magnet 222(shown in FIG. 8) and magnets 204 and 206 (shown in FIG. 7).

In an exemplary embodiment, tip element 210 is laser cut from a materialsuitable for surgical use, such as an electrically conductive,non-corrosive material. In one exemplary embodiment, the material isplatinum. In another exemplary embodiment, the material is stainlesssteel. Projections 232 and recesses 238 of tip element 210 are, in theexemplary embodiment, laser cut out of a cylindrical piece of material.It should be evident that as the number of helices increases in tipelement 210, the flexing capability also increases. In addition, as thepitch of the helix decreases, the ability of tip element 210 to moverelative to itself increases. The flexibility may further be adjusted byproviding different numbers and shapes of projections and recesses toproduce tip assemblies that flex to varying degrees to meet differentobjectives. The combination of the multi-flexing tubing previouslydescribed and independent flexing of the tip assembly 212 isparticularly advantageous for certain applications. For example, RFenergy may be more specifically targeted to desired tissue areas forablation procedures when tip element 212 is flexed than when it is notflexed, and provides a physician with additional positioning capabilityover conventional catheter devices.

In an alternative embodiment, tip assembly includes a plurality ofadjacent rings that extend along longitudinal axis 242. Each ring has adistal side and a proximal side and each side includes alternatingprojections and recesses. This structure provides for flexibility in amanner that is similar to the exemplary embodiment described above. Insuch a configuration, the rings are constructed substantiallyidentically to each other.

Tip assembly 212 is particularly suited for ablation procedures whereinelectrode 208 is energized to deliver radio frequency waves at the siteof an abnormal electrical pathway in the body. Radiofrequency (RF)energy may therefore be applied to biological tissue in proximity to tipassembly 212. Ablation procedures are typically used, for example,within the interior chambers of the heart to thermally ablate cardiactissue. Electrode 208 may additionally be operated to recordintracardiac signals and to provide pacing signals. It should be notedthat tip assembly 212 is also suited for recording of intracardiacsignals and to provide pacing signals. While formed as an integral unit,tip electrode 208 may include multiple electrode elements, such as ringelectrodes for electrophysiological mapping purposes, spaced from oneanother by dielectric materials as is known in the art.

FIG. 10 illustrates a magnet assembly 244 for catheter 200 (shown inFIG. 7). Unlike magnets 106 and 108 (shown in FIG. 1) that arecylindrical in shape and have a constant outer diameter, magnet 204 isoutwardly flared and has a generally ellipsoidal contour. That is, theouter diameter of magnet 204 is largest at an axial midpoint 246 anddecreases from midpoint 246 to opposing ends 248, 250 of magnet 204,providing magnet 204 with a curved profile along an axial length ofmagnet 204.

In one embodiment, magnet 204 is encapsulated in sockets formed intoadjacent tube portions as described above. Alternatively, magnet 204 isencapsulated in a sleeve that extends from the tube portions to covermagnet 204. Similarly to magnets 106 and 108, magnet 204 includes acentral bore through which a tube passes. Magnet 204 is formed from, forexample, neodymium-iron boron-45 (NdFeB-45) into the illustrated shapeor an alternative shape. It should be understood that magnet 206 (shownin FIG. 7) may be formed in the same shape as or a different shape frommagnet 204.

FIG. 11 illustrates a distal portion of catheter 200 in an exemplaryoperating position that shows the deflection of tip assembly 212 andmagnets 204 and 206. By applying magnetic fields to magnets 204 and 206,and also positioning magnet 222 (shown in FIG. 7), the distal portion ofcatheter 200 may be precisely positioned at a specific location withinthe patient's body. The magnetic fields may be generated and controlledby, for example, a magnetic stereotactic system (not shown).

FIG. 12 illustrates a distal portion of an alternative catheter, such asa catheter 260. As illustrated, a distal portion of catheter 260 isshown in an exemplary operating position in which the deflection iscaused by tip assembly 212 and magnets 106 and 108. By applying magneticfields to magnets 106 and 108, and also positioning magnet 222 (shown inFIG. 7), the distal portion of catheter 260 may be precisely positionedat a specific location within the patient's body. The magnetic fieldsmay be generated and controlled by, for example, a magnetic stereotacticsystem (not shown).

The external positioning magnets of catheters 100, 200, and 260 arebelieved to provide manufacturing benefits, and also performancebenefits, in relation to conventional, and more complicated, catheterconstructions for use with stereotactic systems. Larger positioningmagnets are provided for increased magnetic response and performance,and tubing is used that is generally smaller in internal diameter thanthe magnets, thereby resulting in material savings in comparison toknown catheters having larger tubing to accommodate the magnets. Inaddition, increased flexibility is provided. Sockets in the tubesencapsulate the external positioning magnets in a very manufacturableand generally low cost construction. The external positioning magnetsthat are separately provided from the electrode tips also reduce acomplexity and parts count in the tip assembly relative to other knowncatheter tips providing comparable functionality.

FIG. 13 illustrates an exemplary manufacturing process for the magneticguided catheter. Tubing 102 is a unitary tubing that is unitary inconstruction and formed as a single tubing prior to placing the magnetsinside. In an exemplary embodiment, magnets 106 and 108 may be pushedinto tubing 102 during the manufacture process in the directionillustrated by arrow 103. For example, magnets 106 and 108 may bepositioned on mandrels 101 and 105, respectively, and pushed into tubing102 one at a time using a lubricant such as, alcohol, to facilitatereceiving magnets 106 and 108 therein. The alcohol convenientlyevaporates after a short time. Magnets 106 and 108 are shown mounted onmandrels 101 and 105 outside of tubing 102. Magnets 106 and 108 areinserted into tubing 102 one at a time, by pushing mandrels 101 and 105separately and sequentially in the direction of arrow 103.

According to this method, there may exist an interference fit betweenmagnets 106 and 108, and tubing 102, thereby securing the position ofmagnets 106 and 108. It is noted that the drawings are exaggerated tobetter illustrate the interference fit. In reality, the interference fitmay not be as pronounced as it is shown in the drawings. Theinterference fit may be formed by an outer diameter of the at least onemagnet being larger than an inner diameter of the unitary flexibletubing. For example, the interference fit may be formed by magnets 106and 108 having an outer diameter about 0.005 inches larger than theinner diameter of tubing 102.

In another exemplary embodiment, magnets 106 and 108 may be pushed intotubing 102 without any interference fittings. In this embodiment, tubing102 may be wrapped in heat-shrink film or heat-shrink tubing. Theheat-shrink process shrinks the heat-shrink film or tubing around tubing102 so that the position of magnets 106 and 108 is secured within tubing102.

Heat-shrink processes are well understood in the arts. For purposes ofdiscussion, however, the process may implement any of a wide variety ofcommercially available heat shrink film or tubing. Magnets 106 and 108are first positioned within the heat shrink tubing. The magnets arereadily positioned while the heat shrink tubing is in an initial state(e.g., at room temperature) prior to processing. Optionally, the magnetmay be pretreated with a coating, e.g., to reduce the effects ofcorrosion. Application of heat to the heat shrink film or tubing shrinksthe film or tubing around magnets 106 and 108. Shrinkage of the tubingaround the magnet applies the necessary pressure to maintain magnets 106and 108 in the desired position within tubing 102 after the heat shrinkfilm or tubing cools.

Also in exemplary embodiments, catheter 100 can be constructed to havedifferent flexibilities along the length of tubing 102, particularly inthe distal region where the magnets are placed. Typically, portion 126(shown in FIG. 1) between the distal end (where the tip electrode islocated) and first magnet 106 is desired to be the most flexible.Portion 124 between first magnet 106 and second magnet 108 disposedproximally from first magnet 106 is desired to have less flexibility.Still additional portions and additional magnets may be provided, withthe proximal portions having less and less flexibility.

The flexibility can be determined by material properties and/orthickness. Thus, unitary tubing 102 can be made to have varying materialproperties along its length toward the distal end, so that the differentportions will have different flexibilities. The shaft can also decreasein thickness toward the distal end. A thinner wall of tubing 102 resultsin greater flexibility, while a thicker wall of tubing 102 results inless flexibility.

Flexibility can change either continuously/gradually or in abrupt stepsbetween the portions. The abrupt steps may be useful in defining thelocations of the magnets, especially in the embodiment where the magnetsare pushed into the shaft with a lubricant. As magnets 106 and 108 passthrough different flexibility zones defined by abrupt steps, the abruptchange in flexibility provides tactile feedback that magnets 106 and 108are passing from one flexibility zone to another.

The unitary construction of the flexible tubings of catheters 100 and200 is believed to provide manufacturing benefits, and also performancebenefits, in relation to conventional, and more complicated, catheterconstructions for use with stereotactic systems. The catheter can bemanufactured without requiring magnet-shaft fusion and without joints,ensuring high reliability and safety of the catheter. The unitary tubingis easier to manufacture, takes less time to manufacture, and does notrequire an expensive and complicated fusion machine. Eliminating thejunction of the magnet and the shaft also reduces or altogethereliminates undesirable stiffness. In addition, the magnets that areseparately provided from the electrode tips also reduces complexity andparts count in the tip assembly relative to other known catheter tipsproviding comparable functionality. The unitary flexible tubing mayextend along substantially the entire length of the catheter body, andmay have a distal end to be coupled to an electrode assembly and aproximal end to be coupled to a handle. Alternatively, the unitaryflexible tubing may extend along a portion of the catheter body with nofused connections between the magnets, but may be attached to additionalcomponents to form the entire length of the catheter body. For example,the unitary flexible tubing containing the magnets with no fusedconnections may be fused with another flexible tubing to form the entirelength of the catheter body.

FIGS. 14 a-b illustrate another exemplary magnetic guided catheter 300,wherein FIG. 14 b is a magnified view of the distal end portion shown inFIG. 14 a showing exemplary spacing of the magnets 344, 306, and 308 andmultiple sections of shafts numbered with triangle labels.

The exemplary magnetic guided catheter 300 is similar in many aspects tocatheters 100 and 200 described above. Therefore, like components andfeatures of catheters 100 and 200 are indicated with like referencenumbers using the 300-series, and not all reference numbers will bedescribed again for the embodiment 300. Unlike catheters 100 and 200,however, catheter 300 includes different spacing of the magnets (seeFIG. 14 b); and a tip assembly 304 (see FIGS. 16 a-d) is different fromthe tip assembly 104 and distal end portion 202 described above. Otherdifferences are also described in more detail below.

Exemplary single-use magnetically guided catheter 300 generally includesa flexible outer tube, or tubing, 302, a tip assembly 304, threepositioning magnets (344, 306 and 308) separately provided from andspaced from tip assembly 304. Catheter 300 may also include aY-connector 310, and although not shown, a luer device, and anelectrical connector, similar to that described above for catheter 100;to perform, for example, ablation procedures, mapping or pacingprocedures, or to perform other aspects of a medical procedure.

In an exemplary embodiment tubing 302 is fabricated from a tubingmaterial defining a number of portions (see FIG. 14 b). As alreadydescribed above, the different relative lengths of these tube portions,the different flexible properties of tube portions, as well as thenumber and spacing of magnets, allow tip assembly 304 to be moreprecisely positioned within a patient's body, while also avoidingproblems of kinks and excessive deflection of tubing 302 along themajority of its length during use and handling.

In an exemplary embodiment, these portions are fabricated from differentmaterials and grades of materials for enhanced performance of tubing 302in use of catheter assembly 300. The distal flexible portions(non-braided sections) of catheter 300 are manufactured of sixdurometers two French sizes tubing (as opposed to the three durometers,one French size tubing used for catheter 100). This sizing of thecatheter body provides better transition of soft-to-stiff flexibilityand enables the catheter 300 to be more readily pushed during deploymentinto proximity to a volume of target tissue through, for example, arelatively stiff introducer or hollow sheath. Once deployed to alocation near the target tissue(s), the essentially flaccid distal tipportion then can be readily guided by the external magnetic fields of astereotactic system.

Tubing 302 may also be defined by the portions indicated by the numberedtriangles in FIG. 14 b. In an exemplary embodiment, the portions mayhave the following lengths: a first portion (30 mm between adjacentedges of the magnets), a second portion (15 mm between adjacent edges ofthe magnets), as third portion (19 mm), a fourth portion (51 mm), afifth portion (51 mm), and a sixth portion (51 mm). This spacing of themagnets (e.g., about 30 mm-15 mm), has been found to increase theflexibility and maneuverability of the catheter 300, and thus isparticularly desirable in hard-to-reach cardiac anatomical sites. Ofcourse, the invention is not limited to these examples, and otherrelative lengths of the tube portions may likewise be employed in otherembodiments. Likewise, it should be understood that fewer or more tubeportions and magnets could be used without departing from the spirit ofthe described catheter.

Although tubing 302 is shown having separate sections or portions, in anexemplary embodiment, the tubing 302 is formed as a unitary length oftubing. In this regard, the tubing 302 is similar to the tubingdescribed above with reference to FIG. 13. In addition, the magnets 344,306 and 308 may be “pushed” or press-fit into the tubing 302 duringmanufacture, as already described above with reference to FIG. 13.

FIG. 15 a is a cross sectional side view of the distal end portion ofthe magnetic guided catheter shown in FIGS. 14 a-b; and FIG. 15 b is across sectional view taken along lines A-A in FIG. 15 a. FIGS. 16 a and16 b illustrate the distal end portion of the magnetic guided catheter300 shown in FIGS. 14 a-b, wherein (a) is a first perspective view withpartial tip assembly, and (b) is a second perspective view with partialcut-away showing internal detail of a tip electrode 350 where a safetywire 382 may be attached.

In an exemplary embodiment tip assembly 304 includes a tip electrode350, a coupler 352, a band electrode 354, first positioning magnet 344,and a temperature sensor 356 (see FIGS. 16 a-b). Lead wires 358, 360extend to tip electrode 350, and to band electrode 354 on firstrespective ends thereof, and to the connector (e.g., connector 114 shownin FIG. 1) on the second ends so that electrodes 350 and 354 may beenergized by a power source (not shown).

In an exemplary embodiment, tip electrode 350 may be, for example a 7 Frhemispherical-shaped tip electrode that is 4 mm in length. In theexemplary embodiment, tip electrode 350 is fabricated from 90% platinumand 10% iridium, or other materials known in the art such that tipelectrode 350 is viewable under fluoroscopic exposure. While formed asan integral unit, tip electrode 350 may include multiple electrodeelements, such as ring electrodes for electrophysiological mappingpurposes, spaced from one another by dielectric materials as is known inthe art.

Of course, more or less electrodes may be implemented for mapping and/orablation of myocardial tissue. In addition, the catheter may also be‘tracked’ (localized position, configuration of shaft, and/ororientation) using magnetically-activated coils, such as thosecommercially available from Biosense Webster (e.g., the Carto system) orSt. Jude Medical (e.g., the MediGuide magnetic position and orientation,or P&O, system), or with the St. Jude Medical EnSite NavX-compatibleelectrodes disposed along the length of the catheter shaft.

Inner tube 316 forms a fluid lumen which connects directly to aplurality of openings that form irrigation ports 340 (see also FIGS. 16a-b), e.g., for saline irrigation. For example, two rows may be providedhaving six irrigation ports 340 in each row, although otherconfigurations are also contemplated. Inner tube 316 is different thaninner tube 116 in that the inner tube 316 is manufactured with a largerinner diameter/outer diameter (ID/OD) non-braided Pebax tube to providebetter flexibility and lower flow backpressure for proper pumpoperation. This design helps to reduce or altogether eliminate directcontact of saline fluid with the positioning magnet 344, increasingcorrosion-resistance of the magnet 344. Of course, it is noted that thecatheter 300 does not need to be irrigated.

Coupler 352 is also different from the coupler 152 in a number ofaspects. For example, the coupler 352 is not external, but rather isinternal to the catheter shaft. This design reduces machined part cost,and also increases the corrosion-resistance of the magnet 344

In general, the coupler 352 is a cylindrical, electrically nonconductivemember. It is typically made of a polymer such as Polyimide, which isrelatively rigid and has a limited amount of flexibility and resiliencyto form a snap-fit connection, for example. Coupler 352 includes a firstend 370 coupled to the tip electrode 350, and a second end 372 thatallows the magnet 344 to be pressed in partially. The coupler is fittedwithin first end 330 of tube portion 326. Additionally, or alternativelythereto, the first end 370 of coupler 352 is adhered to tip electrode350, and the outer diameter of coupler 352 is adhered to the innerdiameter of tube portion 326. Heat shrink techniques or adhesives mayalso be utilized to permanently attach coupler 352 to tube portion 326and/or tip electrode 350.

Positioning magnet 344 is disposed by pressing in partially at the end372 of coupler 352. The positioning magnet 344 may be manufactured ofany suitable material and have any suitable dimensions. In an exemplaryembodiment, the magnet 344 has a length of 0.375 inches. The 50% lengthincrease in size (as compared to the size of positioning magnet 144)provides higher magnetic deflecting force/moment to the distal portionof catheter 300. In one embodiment, tip positioning magnet 344 is agenerally cylindrical shaped permanent magnet fabricated from a knownmagnetic material, such as neodymium-iron boron-45 (NdFeB-45).Alternatively, magnet 344 is formed from other materials and may haveshapes different from the elongated cylindrical shape illustrated.

A sectional coil spring 380 in the shaft is compressed between any twoadjacent magnets and between the magnet 308 and the fused joint 399 ofshaft tubing 302 (see FIG. 14 b) to help maintain the positions of allmagnets. The compression of each sectional spring serves to reduce shaftkinking tendency during insertion, pushing and deflecting of thecatheter 300 in the patient's body.

As shown in FIGS. 15 a-b and in FIGS. 16 a-b, lead wires 358, 360, and alead wire 378 for the temperature sensor 356 pass through a spacedefined between the inner tubing 316 and the magnet 344. Temperaturesensor 356 is, in one embodiment, a thermocouple type temperaturesensor, and lead wires 358, 360, and 378 are, for example, 38 AWG copperwires having quad polyimide insulation. It is noted that in FIG. 16 b,the temperature sensor 356 and lead wire 378 are shown in the topportion of the figure separately from the electrode tip 350 for purposesof illustration; and also shows lead wire 378 positioned in theelectrode tip 350 (e.g., as illustrated there between by arrow 355).

Catheter 300 may also include a safety wire 382 provided for the tipelectrode 350. The safety wire 382 serves as additional assurance thatthe tip electrode 350 does not disconnect from the catheter 300 when thecatheter 300 is inside of the patient's body. In an exemplaryembodiment, a high tensile strength LCP (liquid crystal polymer) fiberwire may be used as the safety wire 382. One end of the safety wire 382may be affixed in the Y-connector 310, for example, using an anchor pin.The straightness/tension of the safety wire 382 may thus be fine tunedat the catheter handle. The safety wire 382 may also be affixed at theother end to the tip electrode 350. In an exemplary embodiment, thesafety wire 382 is affixed to the tip electrode 350 by tying a knot 384in the end of the safety wire 382 and press-fitting the knotted end intoa hole 386 drilled into the tip electrode 350 (see detail shown withinFIG. 16 b). Adhesive is then applied to bond the knot 384 and wire intothe hole 386 of tip 350.

FIGS. 17 a-c illustrate exemplary assembly of the different sections orportions of the magnetic guided catheter shown in FIGS. 14 a-b. In FIG.17 a, a multiflex shaft 302 is cut, and the larger inner diameter tubingis cut to length. In FIG. 17 b, one end 391 of the cut shaft 302 isflared and the other end 392 of the cut shaft 302 is shaved, as shown inthe detail in FIG. 17 b. Then the flared end 392 is overlapped onto theshaved end 391 of the shaft 302 and fused. In FIG. 17 c, the shaft 302is prepared for assembly to the previously extended multiplex shaft.Additional portions may be similarly joined.

FIGS. 18 a-b illustrate exemplary assembly of magnets in the magneticguided catheter 300 shown in FIGS. 14 a-b. First with reference to FIG.18 a, in step 1, a first spring 380 a is inserted into the shaft 302,followed by the first magnet 308, and each is pushed to a desiredlocation (e.g., distance D1 from the distal end) and oriented with thedesired polarity. In step 2, a second spring 380 b is inserted into theshaft 302, followed by the second magnet 306, and each is pushed to adesired location (e.g., distance D2 from the first magnet 308). Now withreference to FIG. 18 b, in step 3, the positioning magnet 344 is shownas it may be pressed into the coupler 352 to the desired location.Pushing the magnets into the catheter shaft helps ensure that themagnetic strength of the magnet is not degraded by fusion heat. Thesecond end 372 of the coupler 352 is fitted within first end 330 of tubeportion 302. A hole or opening 388 may be formed through one wall of thecatheter shaft and the second end 372 of the coupler 352 to accommodatethe lead wire 360 for the band electrode 354. A thin layer of adhesivemay be applied where the band electrode 354 is to be placed. The distalportion of the catheter tube may then be cut flush with the coupler 352,as shown in FIG. 18 b. A syringe 390 is also illustrated in FIG. 18 b asit may be used to insert an adhesive between the second end 372 of thecoupler 352 and the catheter shaft or tubing 302. It is noted that oneor more of the magnets could be electromagnets that are controllablypole-switched and/or turned magnetically ‘off.’

FIG. 19 illustrates exemplary assembly of a tip electrode 350 to thedistal end portion of the magnetic guided catheter 300 shown in FIGS. 14a-b. In step 1, a one-half inch lumen end is split and the wires arebonded to the split with a one-half inch extra length of safety wire. Instep 2, the flat end of a pull string 386 is bonded to the safety wire.In step 3, a lubricant 388 (e.g., silicon) may be applied to the bondedwires. The top assembly wire is inserted and pulled through the shaft ofthe catheter 300, preferably without any twisting or rotation. Thedistal inner diameter of the shaft may then be cleaned. In step 4, anadhesive may be applied to the tip electrode 350, and the tip electrode350 is then slid onto and mounted to the shaft of the catheter 300.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

What is claimed is:
 1. A catheter comprising: a flexible tubing having aproximal end and a distal end; an electrode assembly attached to thedistal end of the flexible tubing, the electrode assembly including anelectrically conductive tip electrode; a coupler connected between thetip electrode and the distal end of the flexible tubing, the coupler andthe tip electrode being coupled by an interlocking connection having afirst end coupled to the tip electrode and a second end, the couplerconnected to the distal and of the flexible tubing; a first magnetpartially press fit in the second end of the interlocking connection ofthe coupler such that one end of the first magnet extends out of thecoupler; a fluid lumen extending through the flexible tubing to thecoupler, the fluid lumen extending completely through the first magnetand connecting to at least one port formed in the electrode assembly;and a second magnet spaced from the electrode assembly along alongitudinal axis of the tubing; wherein the first magnet and the secondmagnet are responsive to an external magnetic field to selectivelyposition and guide the electrode assembly within a body of a patient. 2.A catheter in accordance with claim 1, wherein the coupler comprises aninternal coupler, and the interlocking connection is formed by couplingan annular projection on the tip electrode and a groove on the coupler,and wherein an adhesive is applied to the interlocking connection.
 3. Acatheter in accordance with claim 1, wherein the interlocking connectionis a snap-fit connection, the interlocking connection press-fit at leastpartially over the first magnet between the first magnet and an innersurface of the flexible tubing.
 4. A catheter in accordance with claim1, wherein the first magnet is disposed in a cavity formed at leastpartially inside the coupler.
 5. A catheter in accordance with claim 4,wherein the electrode assembly further includes a band electrode on anexternal surface of the coupler, the band electrode being spaced fromthe tip electrode and offset from the first magnet.
 6. A catheter inaccordance with claim 1, wherein at least one wire is provided betweenthe fluid lumen and an inner diameter of the first magnet, the at leastone wire being oriented generally in a longitudinal direction.
 7. Acatheter in accordance with claim 1, further comprising a lumen passingthrough the first magnet and the second magnet, and in fluidcommunication with the electrode assembly, wherein the electrodeassembly has at least one row of irrigation ports, the at least one rowhaving at least six irrigation ports.
 8. A catheter in accordance withclaim 7, wherein the electrode assembly has at least a second row ofirrigation ports spaced apart longitudinally from one another, each rowhaving at least six irrigation ports.
 9. A catheter in accordance withclaim 1, wherein the second magnet has an outer diameter greater than afirst outer diameter of the flexible tubing, and wherein the flexibletubing also has a second outer diameter and a third outer diameter, thethird outer diameter being greater than the second outer diameter andoverlying a portion of the second magnet.
 10. A catheter in accordancewith claim 1, further comprising a third magnet separated from thesecond magnet by a first distance along the longitudinal axis of theflexible tubing, wherein the second magnet is spaced from the electrodeassembly by a second distance along the longitudinal axis of theflexible tubing, the first distance being greater than the seconddistance.
 11. A catheter in accordance with claim 1, wherein a portionof the flexible tubing distal to the second magnet is more flexible thananother portion of the flexible tubing proximal to the second magnet.12. A catheter in accordance with claim 1, wherein the flexible tubingcomprises a unitary tubing, and wherein the second magnet is placedinside the flexible tubing after the unitary flexible tubing is formed.13. A catheter in accordance with claim 12, wherein the second magnet ispushed into the unitary flexible tubing with a mechanical interferencefit therebetween.
 14. A catheter in accordance with claim 1, furthercomprising a safety wire coupled at a first end to a handle of thecatheter and coupled at an opposite end to the tip electrode.
 15. Acatheter comprising: a flexible tubing having a proximal end and adistal end; an electrode assembly attached to the distal end of theflexible tubing and including a first magnet at least partially therein,the electrode assembly including an electrically conductive tipelectrode; an internal coupler connected between the tip electrode andthe distal end of the flexible tubing, the internal coupler having afirst end coupled to the tip electrode and a second end, the couplerconnected to the distal end of the flexible tubing, wherein the firstmagnet is partially press fit in the second end of the internal couplersuch that one end of the first magnet extends out of the internalcoupler; and a second magnet spaced from the electrode assembly along alongitudinal axis of the tubing; wherein the flexible tubing is aunitary tubing, and wherein the second magnet is pushed inside theflexible tubing after the unitary flexible tubing is formed; wherein thefirst magnet and the second magnet are responsive to an externalmagnetic field to selectively position and guide the electrode assemblywithin a body of a patient; a lumen passing through the first magnet andthe second magnet, and in fluid communication with the electrodeassembly, wherein the electrode assembly has at least one row ofirrigation ports.
 16. A catheter in accordance with claim 15, wherein aportion of the unitary flexible tubing distal to the second magnetincludes a material which is more flexible than a different material inthe portion of the flexible tubing proximal to the second magnet.
 17. Acatheter in accordance with claim 15, further comprising a third magnetspaced proximally from the second magnet along the longitudinal axis ofthe unitary flexible tubing, the first, second and third magnets beingresponsive to an external magnetic field to selectively position andguide the electrode assembly within a body of a patient.
 18. A catheterin accordance with claim 15, wherein the first magnet is offsetlongitudinally from a band electrode.
 19. A catheter in accordance withclaim 15, further comprising a safety wire connected on one end to ahandle of the catheter and on the opposite end to the tip electrode. 20.A catheter in accordance with claim 19, wherein the safety wire isconnected to the tip electrode by forming a knot in the safety wire andpressing the knotted end of the safety wire into a hole formed in thetip electrode.